Saeed Najafi; Habib Nazarnejad; Hedieh Mohammadnezhad
Abstract
Since most of soil erosion studies in the watersheds are conducted by consultant and executive companies (as contractors) using the semi-quantitative MPSIAC model under the supervision of provincial natural resources and watershed administrations (as employers), so in this study, the results and findings ...
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Since most of soil erosion studies in the watersheds are conducted by consultant and executive companies (as contractors) using the semi-quantitative MPSIAC model under the supervision of provincial natural resources and watershed administrations (as employers), so in this study, the results and findings of the aforesaid studies in West Azerbaijan Province were considered. Analysis of the studies showed that in the last three decades a total of 76 watersheds of the province with an approximate area of 4100 km2 have been studied in terms of soil erosion and sediment yield states using the MPSIAC Model. Estimated mean annual soil erosion was 13.95, 16.30, and 15.59 t.ha−1.yr−1 for northern, central, and southern sections, respectively. Meanwhile, based on the model, the mean sediment yield of mentioned sections has been calculated equal to 5.39, 5.64, and 6.09 t.ha−1.yr−1. Nevertheless, a detailed investigation based on the resistance of different lithology units to erosion in the studied watersheds, as well as land use and vegetation cover as the two most important factors of the MPSIAC Model showed less reliability of the reported results. It seems one of most important reasons for such unreliable results refers to one of the most important weaknesses of the MPSIAC model which estimation of the soil erosion is depended on the estimated amounts of sediment yields and sediment delivery ratio. According to our findings, it can be concluded and suggested that the Forests, Rangelands, and Watershed Management Organization should replace the MPSIAC Model, with USLE family models, especially RUSLE, at least in estimating the soil erosion, in the services description of consultant and executive companies. Implementation of this change should also be taken seriously by the provincial natural resources and watershed management administrations.
Saeed Najafi; Seyed Hamidreza Sadeghi; Tobias Heckmann
Abstract
Comprehensive watershed management programs need to take into account the sediment and related process in sediment management paradigm. Whilst, the dominant processes on sediment yield has not been considered in watershed scale yet. Accordingly, sediment connectivity is an emerging concept in sediment ...
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Comprehensive watershed management programs need to take into account the sediment and related process in sediment management paradigm. Whilst, the dominant processes on sediment yield has not been considered in watershed scale yet. Accordingly, sediment connectivity is an emerging concept in sediment management that has been accounted in recent years to investigate the sediment transfer from different sections of watersheds. Sediment connectivity is defined as the integrated transfer of sediment across all possible sources to all potential sinks in a system over the continuum of detachment, transport and deposition processes. The structural connectivity is therefore a concept derived from sediment connectivity which investigates potential of sediment particles displacement across a watershed on the base of anatomy of watershed's system. Naturally, identifying sectors with similar sediment connectivity patterns support applying similar and integrated sediment control mitigation strategies. The present research was planned to investigate the structural sediment connectivity in Taham Watershed in Zanjan Province for year 2014. To calculate the structural sediment connectivity, the Digital Elevation Model (DEM) and C Factor layers were used and the results were assessed according to field observations and surveying in several times. The results of the validity of the structural sediment connectivity map showed there were acceptable agreement between Field Index of Connectivity (FIC) and Index of Connectivity (IC). In addition, IC map with respective max, min and mean values of 1.02, -8.24 and -5.95, showed 32 percent of the study area had a high structural sediment connectivity that generally have been dispersed in western parts of the study area. Regarding to rapid appraisal and being low cost of IC calculation as well as identification of primary sediment sources, the structural sediment connectivity is a very useful concept for sediment management of watersheds of Iran.
Farzad Bayat Movahhed; Saeed Najafi; Mohammad Roghani
Abstract
Knowledge about optimizing use of rain water under different systems for overcoming water stresses, maximization of crop yield and how their effects is very important. So in this research effect of Rain Water Catchment (RWC) systems under five treatments viz. control (A), eliminated of vegetation and ...
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Knowledge about optimizing use of rain water under different systems for overcoming water stresses, maximization of crop yield and how their effects is very important. So in this research effect of Rain Water Catchment (RWC) systems under five treatments viz. control (A), eliminated of vegetation and pebble with a gravel filter (B), eliminated of vegetation and pebble without any gravel filter (C), insulated some portion by plastic with gravel filter (D) and insulated some portion by plastic without any gravel filter (E) on activity of photosynthetic parameters have been assessed. The research was conducted in a randomized complete block design with 3 replications for each treatment. RWCs were designed in 8, 5, and 0.5 meters for the length, width and depth respectively, as well as with 9 % downward slope. To facilitate runoff infiltration in root region; a gravel filter was created that was 10 cm diameter and 30 cm depth respectively, in all treatment. Four photosynthetic factor viz. Photosynthetic rate per unit leaf area, stomatal conductance, transpiration rate and substomatal CO2 adsorption were measured after 10 and 23 days after one rainfall event in 2011. Results showed there are significant differences between measured factors except substomatal CO2 adsorption under different treatments. Totally results of this research showed that two Rain Water Catchment systems including insulated some portion by plastic without any gravel filter (E) and eliminated of vegetation and pebble without any gravel filter (C) had maximum positive effect on activity of photosynthetic parameters in Apricot seedlings versus control treatment (A) exhibited minimum activity of photosynthetic parameters in Apricot seedlings. It can say the effect of treatments in runoff delivery to the Apricot seedlings is the cause of obtained aforementioned results.
